How can I apply textures in Blenders UV Editor
You may try using a Stencil mapping option. In UV Editor set the mode to Paint. Add two textures in a Texture panel using the '+' button. Change the brush mapping type to Stencil.


Your texture stencil should appear. Press Image Aspect button to get the original picture dimensions. Hold Ctrl+RMB to rotate stencil, Shift+RMB to change its size and RMB to pan it. Then paint.


Click on the texture preview window, choose your second texture (Up/Down Arrow, Enter or choose it from the textures list) and paint again.


You can use the same method in a 3D View window. It's very useful for blending/hiding the seams btw.